I own nothing but the bizarre brain that came up with this drabble. This story is just pretty much the result of a weekend reading the old Doctor Who book Lungbarrow and rewatching the season 1 DVDs, as well as a bet placed by a friend that I couldn't write a fanfic. Well at least she didn't say it had to be any good, since I don't have much in the way of writing talent.
The Doctor gently lowered Rose to the ground before rising to face the Tardis. Desperate to release the Time Vortex back into the heart of the Tardis. All it took was mere seconds, but those seconds where more than enough.
He could feel the energy of the Time Vortex burning inside, expanding his knowledge and vision beyond just the fields of probability and the sense of time and space that was part of being a Time Lord. He could also feel the latent sentience in that energy reaching out to him. It was the sentience that belonged to the Tardis, the sentience that had possessed Rose to complete a common goal... to save him, the sentience that now showed him in a second that stretched out to eternity the repercussions of all they had done with a gift given out of love.
As the Doctor was guided in his new limitless vision he saw something that no Time Lord had ever seen before. His life beyond and before his first incarnation before this series of regenerations. He saw a life that he had always felt a part of before, a life that had been hinted at before in his very DNA and had guided his need to hide who he was. He saw Jack.
A desire in Rose to make sure Jack lived; combined with the Roses and the Tardis' desire to never see him die gave Jack more life than he would ever wish to see, it cursed him with immortality. Yet it also created a necessary paradox. Jack, poor Jack, would now be cursed to live for millennia on the slow path of life on earth. Until one day close to the time period he was born in Jack finally would feel the need to abandon his home planet and travel.
Jack would travel far and wide in time and space until he reached a small chaotic planet with a leader named Rassilon trying to unite his people and a brilliant, ill fated, engineer named Omega trying to bring them a new power. He would settle there and throw in his lot with them, giving them all the knowledge he had collected on time travel becoming the third unrecorded founder of this new society, Gallifrey and the birth of the Time Lords.
Until one day Jack finally discovered a way to end his curse and eventually implemented it after Omega became lost, and Rassilon power hungry. He found a way to die, even if it was just temporary. He released his essence into the genetic wellspring of the Time Lords to be reborn. Reborn as him.
Along with his past's fate the Doctor could also see echoes of his future. That along with his sentimental ties to earth and his desire to never be stuck living on the slow path in one place again; Jack's curse of immortality had also carried over. He wouldn't just see the 12 regenerations of a normal Time Lord, he would regenerate indefinitely. As long as time existed he would exist. The lonely God! He had to laugh, and in his head he did.
As the second passed and he released Time Vortex, its mission to show him what he needed to see complete, he spared a thought for Jack, poor Jack. He new he had to leave him here, and not just because it was seen as part of his life. With all that had occurred he would never feel comfortable in Jacks company again for long periods of time, he was a fixed point in his time like a previous regeneration.
As the transfer was complete and the Tardis door closed the Doctor stumbled a little and then smiled. He could feel the damage left behind and a regeneration coming. He really needed to develop a more lassie fair personality with his next regeneration or he would go crazy with the knowledge he'd been left with. At least for now he had no time to brood. He needed to get Rose back into the Tardis and take off. He also needed to try to hold off this regeneration until she regained consciousness. She would need some type of explanation of what was to come and this would probably keep her from asking too many questions about Jack's fate.